Abstract and Project Summary Fragile X Syndrome (FXS) is a leading inherit cause of intellectual disability. The goal of this project is to develop effective medications to improve conditions of FXS. The proposed research is based on the hypothesis that a combined administration of ACT01 and DHA to the Fmr1 KO mice, a mouse model of FXS, will rescue brain development. The hypothesis is based on experimental observations that dopaminergic deficit and adrenergic excess are involved in the delayed Fmr1 KO brain development. ACT01 is a dopamine reuptake specific blocker capable of reversing DA deficit; DHA is an n-3 fatty acid reportedly capable of attenuating excessive norepinephrine actions. DA and DHA are required for brain functions. ACT01 and DHA combination should restore catecholaminergic balance and rescue brain development. The research will characterize the effects of ACT01, DHA, and their combination, on behaviors and blood and cerebral biochemistries. The behavior research examines the effects of each agent and their combination behaviors associated with different brain regions. The blood biochemistry characterizes the effects of ACT01, DHA, and their combination on catecholaminergic regulated lipid and glucose metabolic balances. Studying these metabolic activities as biomarkers is a mean to assess these agents' targeted (catecholaminergic activities) engagements. The cerebral biochemistry focuses on examining expression levels of neuronal and astrocytic proteins (e.g., glucose transporters) down stream from respective mTOR pathways of different cells. Catecholamines take part in regulating the balanced expressions of these proteins during brain maturation process. Combination of ACT01 and DHA should help to restored DA-NE balance. Restored catecholaminergic homeostasis should rescue behavior, normalize metabolic activities, and restore the neuronal-astrocytic balance. Completion of these studies will provide a coherent body of proof-of-concept experimental evidence to support our goal of providing effective therapeutic for FXS.